Radical reactions are one of the most useful methods for organic synthesis. Therefore, the study on the novel radical reactions with hypervalent iodine compounds has been carried out. Here, based on our study, the formation of carbon-centered radicals, oxygen-centered radicals, and nitrogen-centered radicals with hypervalent iodine compounds has been established. Especially, the formation of nitrogen-centered radicals from sulfonamides with hypervalent iodine compounds is very useful for the preparation of 1,2,3,4-tetrahydroquinoline derivatives and saccharin derivatives. Then, the present method was applied for the preparation of the key skeletons of biologically active compounds. These results were published in five international Journals and other three papers are in press.